Proton-induced switching of metal-metal interactions in dinuclear ruthenium and osmium complexes bridged by 2,2[prime]-bis(2-pyridyl)bibenzimidazole

Journal Article · Wed Oct 02 04:00:00 EDT 1991 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00020a014· OSTI ID:6769941

Haga, Masaaki; Ano, Tomoaki ^[1]; Kano, Kenji ^[2]; Yamabe, Shinichi ^[3]

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1. Mie Univ. (Japan)
2. Gifu Pharmaceutical Univ. (Japan)
3. Nara Univ. of Education, (Japan)

New dinuclear complexes [M(L)[sub 2](bpbimH[sub 2])M(L)[sub 2]][sup 4+] (M = Ru, Os; L = bpy, phen; bpbimH[sub 2] = 2,2[prime]-bis(2-pyridyl)bibenzimidazole) act as dibasic acids. Both the absorption spectra and oxidation potentials are strongly dependent on the solution pH, which is responsible for the deprotonation of the N-H group on the coordinated bridging ligand. The pK[sub a] values reflect the metal oxidation states, M(II) and M(III). The pK[sub a] values of the mixed-valence dinuclear complexes are quite close to those of each M(II) and M(III) component, which suggests that mixed-valence complexes bridged by the protonated ligand bpbimH[sub 2] exhibit the intervalence (IT) band at 7300 cm[sup [minus]1] for M = Ru and at 9100 cm[sup [minus]1] for M = Os, respectively. When the bridging ligand is deprotonated, this IT band is shifted to lower energy at 5880 cm[sup [minus]1] for M = Ru and 7700 cm[sup [minus]1] for M = Os and intensified. The degree of metal-metal interaction of the deprotonated dinuclear complexes becomes 4-6 times larger than that of the protonated complexes. This proton-induced change of metal-metal interaction can be rationalized by change of HOMO energy levels on deprotonation or protonation in the bridging ligands. Thus, proton transfer in the bpbimH[sub 2] bridging dinuclear complexes can be utilized to serve as a trigger signal for switching the metal-metal interaction.

• OSTI ID: 6769941
• Journal Information: Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 30:20; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
AZOLES
COMPLEXES
ELECTRONIC STRUCTURE
HETEROCYCLIC COMPOUNDS
IMIDAZOLES
INFRARED SPECTRA
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OSMIUM COMPLEXES
PH VALUE
REDOX POTENTIAL
RUTHENIUM COMPLEXES
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
VALENCE
VISIBLE SPECTRA